At normal conditions, blood flows in large conduits of the vascular system (i.e., veins and arteries) in an unhindered non-turbulent manner. On some occasions, for example during vascular related illness or after surgery, a local change to blood vessel cross section and/or an introduction of a new opening along its periphery (e.g., as result of a bypassing graft), will cause an immediate change to the original local flow regime, thereby creating “stagnant areas” in which pressures are substantially low and flow is minimal or even absent, and/or “turbulent areas” in which pressures are substantially high and turbulent flow occurs. A healthy vessel will then undergo a prolonged process of local remodeling and/or reshaping that in some circumstances will lead to severe cases of vessel obstruction and/or organ failure.
In surgical jargon, an anastomosis commonly relates to the joining together of two hollow organs, such as a vein to an artery. Anastomoses may be performed end-to-end, side-to-side or end-to-side depending on the circumstances of the required reconstruction or bypass. Anastomoses are typically performed on arteries and veins, including most vascular procedures such as all arterial bypass operations (e.g. coronary artery bypass). Patients with end stage renal disease undergo frequent hemodialysis to remove toxins from the blood and maintain appropriate homeostasis. In dialysis, blood is withdrawn from a vascular access, purified, and returned to a vein or a synthetic graft.
The most common form designed to enable long-term vascular access in chronic hemodialysis patients is the native arteriovenous (AV) fistula.
In the AV fistula method, openings are created in an artery and vein, usually in the arm above or below the elbow. The borders of the openings are attached, to create a fistula. The arterial blood pressure, being higher than the venous pressure, together with the supra-physiological flow rates, eventually enlarges the vein and a “mature” and a functioning vascular access is created 2-4 months post procedure. The mature vascular access enables sufficient blood flow rate, effective dialysis procedure and the accommodation of a cannula or large needles.
Hemodialysis vascular access dysfunction is the single most important cause of morbidity in the hemodialysis. According to Roy-Chaudhury et al., “Vascular access in hemodialysis: issues, management, and emerging concepts” (in Cardiology Clinics 23, 2005: 249-223) there are several causes of failures of vascular access procedures.
In the AV fistula Roy-Chaudhury et al. identify the two main causes of such failure as being early maturation failure and late venous stenosis, both caused by neointimal hyperplasia.
Early maturation failure is usually caused by the development of a juxta-anastomotic stenosis due to neointimal hyperplasia in propinquity to the artery-vein anastomosis.
Hence, there is a need for an advantageous method and/or apparatus for alleviating, or preventing anastomotic dysfunction or failure.
It may be desired to reduce, minimize or prevent the buildup of neointimal hyperplasia. It may alternatively or in addition be desired to reduce, minimize or prevent vascular constriction and/or luminal stenosis, e.g. resulting from neointimal hyperplasia.
It may alternatively or in addition be desired in certain cases to prevent, minimize or eliminate hemodialysis vascular access dysfunction.